Z-Pinches In The Western Part Of The United States
Z-Pinches in the Western Part ofthe United StatesRobert A. Schill, Jr.University of Nevada, Las VegasDept. of Electrical and Computer Engineering4505 Maryland Parkway; Box 454026Las Vegas, NV 89154-4026(702) 895-1526/4183 Lab: (702) 895-1430FAX: (702) 895-4075e-mail: schill@ee.unlv.eduURL: http://www.ee.unlv.edu/ schill
References and Special Thanks Special Thanks Dr. John Maenchen & Dr. David Johnson, Radiographic Physics Dept. - SNL Dr. Rick Spielman, High Energy Plasma Physics - SNL Dr. Bruno Bauer & Dr. Victor Kantsyrev, Physics, University of Nevada, Reno Dr. Frank Wessel, Physics, University of California, Irvine Dr. H.U. Rahman, Physics, University of California, Riverside Dr. John DeGroot, Physics, University of California, Davis Dr. David Scudder & Dr. Jack Schlachter, Los Alamos National Laboratory Gordon MacLeod & Sheldon Freid, Bechtel NevadaInteresting References ABCs of Zs: Z-Pinch Technology Workshop Proc., May 21-22,1998. G. Yonas, Fusion and the Z Pinch, Scientific American, Aug. 1998. K. Matzen, Z Pinches as Intense X-Ray Sources for High-Energy Density Physics Applications, Physics of Plasmas, 4 (5), 1997, pp.1519.Ronald Riley, Jr., Instability Heating of Solid Fiber Z-Pinches, thesis , Univ. CaliforniaSan Diego, 1993.D. Mosher, Phy. & Tech. of Z-Pinches, US Part. Accel. Sch., Berkeley, CA, Jan. 1997.Robert A. Schill. Jr., UNLVUniversity of Wisconsin, Madison [Oct. 12, 1998]2
Flow DiagramDifferencesZOTStaged ZPinchNTF HDZP IIWhy All The Interest?ZZ PINCHESPINCHESIssues?MechanismsBrief History.What?Motivation?ComponentsNTF - Nevada Terawatt FacilityPBFA Z - Particle Beam Fusion Accel. ZZOT - UC IrvineRobert A. Schill. Jr., UNLVSandia Nat. LabPBFA ZUniversity of Wisconsin, Madison [Oct. 12, 1998]3
Z-Pinch Effect Z-Pinch Geometry Plasma columnLarge current flow along its longitudinal axis Current generates a large magnetic fieldMagnetic field in turn interacts with the local currentBy a Lorentz force (J x B), radial confinement or a radialcompressionMagnetic energy concentrated near plasma surface; efficient Mechanism Instabilities - Currents seek paths of low inductance dI/dt V/L; Coaxial geom. with rigid return -- L ln(rc/r) NOTE: NO External Coils!!!Robert A. Schill. Jr., UNLVSIMPLICITY!?!?University of Wisconsin, Madison [Oct. 12, 1998]4
Graphical Picture of the Z-Pinch EffectJxBBRigid ReturnConductorIIrBIrcPlasmaJxBPlasmaZ-Pinch MechanismRobert A. Schill. Jr., UNLVZ-Pinch Coaxial GeometryUniversity of Wisconsin, Madison [Oct. 12, 1998]5
Artist’s View of the Radiation from a Z-PinchRobert A. Schill. Jr., UNLVUniversity of Wisconsin, Madison [Oct. 12, 1998]6
Brief Historical Background 1934 Bennett -- (Bennett Pinch - Equilibrium) W.H. Bennett, “Magnetically Self Focusing Streams,”Phys. Rev. 45, (1934), p. 890-897.Plasmas thermal and magnetic pressures are balanced. Easy to build & operate but NOT a promising approachTestbed for plasma physics and plasma diagnostic dev. Shock-Heated Z PinchResistive Heated Z PinchGas-Embedded Z Pinch Around 1950; Pinch Exp. for B-Confined Fusion Niche in Material Radiation Studies Z-Pinch Classifications (Non-Equilibrium Pinch)Robert A. Schill. Jr., UNLVUniversity of Wisconsin, Madison [Oct. 12, 1998]7
What’s the Problem? Early Shock-Heated Pinch Exp. (Snowplow) Low density gas & large pulsed voltage supplied by Inductive storage device Capacitive storage deviceRequired electric field needed 1.6 MV/mAchieved only 0.1 MV/mFLASH OVER Problem - surface becomes ionized by highvoltage allowing current to arc & hence short out Early Resistively Heated Pinch Experiments Current carrying electrons being slowed by ion collisionsResistance T-3/2 ; less effective at high temperaturesSimple pinch is unstableRobert A. Schill. Jr., UNLVUniversity of Wisconsin, Madison [Oct. 12, 1998]8
What’s the Problem? (conti.) Early Gas Embedded Z Pinch Z-pinch is initiated in a narrow column immersed in amedium of neutral gas ( 1960) Inhibit wall impurities in the plasma Suppress some instabilities by inertially coupling the pinch to theionized corona around the pinch Column expansion was driven by an accretion of neutral gassurrounding the pinch which increased the pinch line densityand cooled the plasma ( 1982)Suggested solution was to increase the current rise rate Instabilities -- non-uniform compression for req. time scaleState of the art in pulse power not mature Summarized Major Problems in Early DaysRobert A. Schill. Jr., UNLVUniversity of Wisconsin, Madison [Oct. 12, 1998]9
Z-Pinches Throughout the United StatesRobert A. Schill. Jr., UNLVUniversity of Wisconsin, Madison [Oct. 12, 1998]10
Motivation & Goals Driving Z-Pinch Exp. Mid 1960’s to 1990’s Limited power output for fusion race -- 10-3 TW ( mid 1960s)Focus on optimizing subkiloelectron-volt X-ray output(Nuclear weapon) Radiation studies on materials & electronics 1-5 keV Spectral region: radiation-material interaction studiesSimulate different stages of a nuclear explosion Emphasis - generation of softer X-rays that can be thermalized Pulse power - charged particles (electrons 70s, ions 80s, X-rays 90s) Ablator physics and radiation symmetrization experiments Radiation-Materials & Stockpile Stewardship - Present Inertial Confinement Fusion [ICF](Origins ’73) - Present Applications in Shock Physics & Astrophysics - PresentRobert A. Schill. Jr., UNLVUniversity of Wisconsin, Madison [Oct. 12, 1998]11
Specific Energy Densities Explosives Bituminous Coal Natural Gas Crude Oil D-T FusionRobert A. Schill. Jr., UNLV4 x 103 J/gm22 x 103 J/gm35 x 103 J/gm36 x 103 J/gm2 x 1010 J/gmUniversity of Wisconsin, Madison [Oct. 12, 1998]12
Fusion Process Forcing together Deuterium and Tritium nucleiFuse into a form of HeliumEmits large amount of energyPellet must be squeezed uniformly to high density for afusion reaction to ignite and burn - Major ProblemRobert A. Schill. Jr., UNLVUniversity of Wisconsin, Madison [Oct. 12, 1998]13
ICF Uses the Principle of the Hydrogen BombPRIMARY (FISSION DETONATOR)PRIMARY MTRITIUMPELLETRADIATIONTUNGSTENWIREARRAYSECONDARY (FUSION FUEL)HYDROGEN BOMBRobert A. Schill. Jr., UNLVPRIMARY HOHLRAUMPROPOSED FUSION REACTION CHAMBERSUniversity of Wisconsin, Madison [Oct. 12, 1998]14
The Inertial Confinement Fusion ConceptLaser FusionLaser energyBlowoffInward transportedthermal energyAtmosphereformationCompressionLaser beams rapidlyheat the surface of thefusion target forminga surrounding plasmaenvelope.Fuel is compressed bythe rocket-like blowoffof the hot surfacematerial.Robert A. Schill. Jr., UNLVIgnitionDuring the final part ofthe laser pulse, the fuelcore reaches 20 times thedensity of lead and ignitesat 100,000,000oC.University of Wisconsin, Madison [Oct. 12, 1998]BurnThermonuclear burnspreads rapidly throughthe compressed fuel,yielding many times theinput energy.15
Inertial Confinement Fusion (ICF) RequirementsPulsed Power FusionPellet implodes to 1/1000 to 1/10,000of its original volume, fusionbegins as temperature reachesX-rays vaporize outer layer of fuelWavefront of burning hydrogen120 million degrees or more.pellet which bursts outward andexpands outward and cools untilimparts inward momentum to thefusion ceases.hydrogen fuel. Ignition Requirements - Laser or Pulse Power 500 TW2 MJ of X-ray radiation at 3 million degrees4 nsPellet size --- .Robert A. Schill. Jr., UNLVUniversity of Wisconsin, Madison [Oct. 12, 1998]16
Fusion Experiment Alternatives Magnetic Confinement -- Tokamak Magnetic field confines the energy and particles (traps hotdeuterium-tritium plasma statistically long enough for fusion) International Thermonuclear Exp. Reactor (ITER) - 6 to 10 B Break-even? - Techn. and political diff. (US, Japan, Europe, Russia) Inertial Confinement -- Laser Fusion Inertia confines the energy and particles (lasers used to heatthe fusion fuel, blow-off results causing the pellet to implode) National Ignition Facility (NIF) - 1.2 B Ignition - 0.1% to 0.5 % equivalent efficiency due to laser technology Magnetic Insulation - Inertial Confinement -- Z Pinch B-field confines the energy and inertia confines the particles X1 Facility - 0.4 B (Note: Z’s equiv. eff. is 15%; X1’s equiv. eff. ?) HIGH YIELD - fusion energy output energy input to the systemRobert A. Schill. Jr., UNLVUniversity of Wisconsin, Madison [Oct. 12, 1998]17
US Z-Pinch Programs Directed Towards Weapons& ICF R&D Diagnose Intense X-Ray Sources DOD & DOE Nuclear Weapons Effects Sim. (NWES) X-rays in the 1 keV and above regime to study transientresponse and damage due to exo-atmospheric nuclear bursts DOE Weapons Physics (WP) and ICF Programs Soft X-rays below 1 keV Radiation transport and trapping Equation of state Opacity properties of high energy density matter X-ray Diagnostics Study initiation and evolution of imploding pinches-optimizeX-ray performanceMaterial response to X-ray heatingRobert A. Schill. Jr., UNLVUniversity of Wisconsin, Madison [Oct. 12, 1998]18
Z-Pinch Advances at Sandia National Lab. Saturn (1996) Input: 10 MA, 20 TWOut: 40 TW (90 wire array) Input: 20 MA, 50 TW,25 TW/cm2, few nsOutput: 3MJ, 290 TW1.8 million deg. ( 233 eV) PBFA Z or Z X1 Robert A. Schill. Jr., UNLV(High yield)Input: 60 MA, 150 TW,75 TW/cm2, 10nsOutput: 16 MJ, 103 TW3 million deg. ( 390 eV) University of Wisconsin, Madison [Oct. 12, 1998]19
Cartoon Picture of PBFA-Z or ZRobert A. Schill. Jr., UNLVUniversity of Wisconsin, Madison [Oct. 12, 1998]20
PBFA-Z or ZRobert A. Schill. Jr., UNLVUniversity of Wisconsin, Madison [Oct. 12, 1998]21
Building a Wire Array - Close-Up View Wire Array - Single/Double 1/10 th Dia. human hair0.7 microns thickArray dia. shot glass Trial & error approach Al, Ti, Cu, W (Tungsten)K Shell Rad. & Rad. Emissivity Wire Material Wire Placement Robert A. Schill. Jr., UNLVSymmetry - crucialSmall interwire spacing - cont.plasma shellUniversity of Wisconsin, Madison [Oct. 12, 1998]22
Experimental Setup of Double Nested WireArraysRobert A. Schill. Jr., UNLVUniversity of Wisconsin, Madison [Oct. 12, 1998]23
Close-Up View of a Double Nest Wire ArrayRobert A. Schill. Jr., UNLVUniversity of Wisconsin, Madison [Oct. 12, 1998]24
The Hohlraum - Vacuum Hohlraum Radiation chamber-X-ray oven Composite -Gold Coated Chamber High Z (atomic number) lined material Secondary Hohlraums - Physics FactoriesRobert A. Schill. Jr., UNLVUniversity of Wisconsin, Madison [Oct. 12, 1998]25
Target Concepts for X1 - Hohlraum Types Dynamic Hohlraum (a) High Z imploding plasma shellstagnates on an inner low Zcylinder (foam)Plasma stagnates in the low ZRadiation permeates low ZOuter cooler regions ofimploding plasma act as a highZ hohlraum wall Static-Walled Hohlraum (b) Robert A. Schill. Jr., UNLVDynamic hohlraum conceptMin. capsule preheat atexpense of x-ray drive eff.University of Wisconsin, Madison [Oct. 12, 1998]26
Temperatures for 90 TW Pinch Power Computer Simulation Temp. (eV) Nonuniformity: due to sec. hohlraum Measure nonuniformity of rad. field Active Shock Breakout Diagnos. VISAR - Velocity InterferometryRobert A. Schill. Jr., UNLV Al/LiF VISAR sample 1.2 MbarsUniversity of Wisconsin, Madison [Oct. 12, 1998]27
Magnetically Insulated VacuumTransmission Line - MITLHigh E-field vacuum systems emit electrons above 250 kV/cmMITLs use the aximuthal magnetic field generated behind theleading edge of the high current power pulse to trap subsequentelectrons into high efficiency (low loss) insulated flowThis technique has been in constant use since the 1960sAnodePulse FrontElectron LeakageCurrentTrapped Electron SheathC.L.Robert A. Schill. Jr., UNLVCathodeSelfMagneticFieldUniversity of Wisconsin, Madison [Oct. 12, 1998]28
Standard Pulsed Power Components - Marx Banks,Intermediate Store, Pulse Forming LinesRobert A. Schill. Jr., UNLVUniversity of Wisconsin, Madison [Oct. 12, 1998]29
Typical Closing SwitchPos.WaterNeg.Robert A. Schill. Jr., UNLVOilSF6University of Wisconsin, Madison [Oct. 12, 1998]SF630
Equipotential Plots for Typical Closing SwitchesRobert A. Schill. Jr., UNLVUniversity of Wisconsin, Madison [Oct. 12, 1998]31
ARCS AND SPARKS: OPEN SHUTTER PICTURE OF ZRobert A. Schill. Jr., UNLVUniversity of Wisconsin, Madison [Oct. 12, 1998]32
X-Ray Pinhole Images on Nested Shot 180 Experimental DataPinchCompression 40 to 1 Tightest pinchachieved on Z 1 mm diameter1 ns intervalsRobert A. Schill. Jr., UNLVUniversity of Wisconsin, Madison [Oct. 12, 1998]33
Why does Z appear to be so Successful?What is its Secret to Success? Instability Problems Addressed? Pulse Power Problems Addressed?Secret to Success Robert A. Schill. Jr., UNLVMITL - Magnetically InsulatedTransmission LinesExtract the energy quickly, form ofx-rays, before instabilities destroythe pinch geometry (FAST PINCHMachine)MachineMore thin wires in array allows fora more uniform plasma pinchUniversity of Wisconsin, Madison [Oct. 12, 1998]34
Nevada Terawatt Facility - University ofNevada, Reno High Density Z Pinch - II(HDZP-II) Existed at Los Alamos National LaboratoryMoved to Reno in Summer 1998Smaller Pinch - Couple of Terawatts Z studies at Sandia Limited to about 200 shots / yr Difficult to study pinch properties due to tremendous Purposeenergies/powers generated Will fill a need for short-pulse, high power, low cost zpinch with good diagnostics and high repetition rate.Robert A. Schill. Jr., UNLVUniversity of Wisconsin, Madison [Oct. 12, 1998]35
High Density Z Pinch - II (HDZP-II)Robert A. Schill. Jr., UNLVUniversity of Wisconsin, Madison [Oct. 12, 1998]36
HDZP-II Uses Three Stages of PulseCompression Pulse power depends on the fast rise time of the current tothe load. Induction effects hinder ideal pulse poweroperations and need to be minimized.Robert A. Schill. Jr., UNLVUniversity of Wisconsin, Madison [Oct. 12, 1998]37
Staged Z-Pinch: University of California, Irvine Laboratory Facility Name: ZOT Projected to Achieve Break-even Fusion in aCompact Laboratory Device Two Dim codes suggest that ignition and near unityyield is possible in a staged Z-pinch driven by 50 kJenergy bankDefinitive experiments have not been performed to date MHD instability time scales are important Slow Pinch Machine Low Cost, Low Maintenance MachineRobert A. Schill. Jr., UNLVUniversity of Wisconsin, Madison [Oct. 12, 1998]38
What Is Meant By “Staged”? Objective is StableEnergy and PowerCompression to ner(z-pinch)Robert A. Schill. Jr., UNLVanodeco-axialtarget(fibertarget)Helmholtzcoils Energy is coupled instages Pulse power driver Imploding liner pinch “Squeezes” magnetic field linesHeats prepulsed DTfiber targetPinch is multi-shellconfigurationUniversity of Wisconsin, Madison [Oct. 12, 1998]39
Stabilization of Linear PinchEnd-On Kerr Cell PhotosRobert A. Schill. Jr., UNLVUniversity of Wisconsin, Madison [Oct. 12, 1998]40
2-D Illustration of Staged Z-Pinch Facilityand Discharge-Load RegionTo Cryogenic ExtruderCapacitorBankHigh PressureGas ValveCryogenicExtruderH.V. InterfaceRail GapSwitchesDiagnosticWindowsBzCoilsHigh DensityPlasma InjectorVacuumPumps16 PlasmaGun ArrayHigh PressureGas ValveToVacuum PumpsHigh DensityPlasma InjectorRobert A. Schill. Jr., UNLVUniversity of Wisconsin, Madison [Oct. 12, 1998]41
3-D View of Staged Pinch Facility3mRobert A. Schill. Jr., UNLVUniversity of Wisconsin, Madison [Oct. 12, 1998]42
Vacuum Load Region Underside of Staged Z DeviceZ-Pinch VacuumChamber Anode-cathodegap is 15 mmIsc 2 MAQuarter periodrise time 1.8 µs Vacuum PumpsRobert A. Schill. Jr., UNLVUniversity of Wisconsin, Madison [Oct. 12, 1998]43
Upper Deck Load Region Maxwell Rail Gap SwitchesPlate TransmissionLine (1.25 m x 2.0 m) 6.4 mm thick Al platesInsulated 1.8 mm thickmylar film Capacitor Banks Robert A. Schill. Jr., UNLV2 sets of Cap. bankseach consisting of ten2.5µF, 50 kV Cap.University of Wisconsin, Madison [Oct. 12, 1998]44
Cryogenic Extruder Deuterium Fibers areExtruded Robert A. Schill. Jr., UNLVDeuterium freezes at 14 KIn vacuum it can “live” atroom temperature Transparent to roomtemperature infrared Fiber diameters 110 to130 µm Gravity is used to maintaina vertical orientation of thefiber in the Z pinchchamberUniversity of Wisconsin, Madison [Oct. 12, 1998]45
What Are The Key Mechanisms? Staging Process Coupling of energy in differentstages. Non-equilibrium, TransientlyStabilized, Composite Pinch Robert A. Schill. Jr., UNLVTwo plasmas employed.Dynamic magnetic compressioninhibits the instability process.Simulations have shownmicrosecond orders in stability.Compressing the magnetic fieldincreases the implosion timecompared to Fast Pinches.University of Wisconsin, Madison [Oct. 12, 1998]46
Conclusion Z-Pinches May Be Used As A Testbed For Plasma Experiments and DiagnosticsZ-Pinches Are Now Strong Contenders In TheFusion RaceZ-Pinches Are Useful Tools In The StockpileStewardship And Nuclear Weapons ProgramsSomeday, Compact University ICF LaboratoryReactors May Be FeasibleRobert A. Schill. Jr., UNLVUniversity of Wisconsin, Madison [Oct. 12, 1998]47
Robert A. Schill. Jr., UNLV University of Wisconsin, Madison [Oct. 12, 1998] 2 References and Special Thanks Special Thanks Dr. John Maenchen & Dr. David Johnson, Radiographic Physics Dept. - SNL Dr. Rick Spielman, High Energy Plasma Physics - SNL Dr. Bruno Bauer & Dr. Victor Kantsyrev, Physics,
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